The need for proper fitness has long been recognized to help maintain a long and healthy life. Many people have purchased dumbbells to aid in their fitness training. Dumbbells are typically held in one hand during performance of a fitness exercise. A common dumbbell includes a central portion, to be grasped a user's hand, and axial ends for receiving weight plates. A shoulder separates the central portion from each of its axial ends and provides a stop for receiving the weight plates.
Commonly, the axial ends of the dumbbell are externally-threaded for forming a threaded connection with the internal threads of a threaded collar. As such, when one or more weight plates are disposed on the axial ends of the dumbbell, the weight plates can be held between the shoulder and the collar by the threaded engagement of the collar to the threaded axial end. A convenience of the above described dumbbell is that different numbers and/or weights of weight plates can be attached to the dumbbell so that the weight of the dumbbell can be changed to different desired weights without the need for purchases multiple dumbbells.
A deficiency of common dumbbells, however, is that they are short and designed for manipulation by a single hand. Thus many exercises, which require and/or are facilitated by an elongated bar which may be grasped by two hands that are approximately a shoulder width apart, cannot be performed by typical dumbbells. Thus, a user is often required to purchase or obtain another weight system that includes an elongated bar. Having to purchase another exercise system with matching weights can be cumbersome and expensive.
Weight bars have been proposed with brackets at their axial ends to attach dumbbells, but these designs are cumbersome and do not utilize the existing externally-threaded ends of typical dumbbells. Some proposed designs have weight bars with threaded ends, but the thread designs on these bars is such that the bar can only be used with a specifically matched set of dumbbells having a specifically matched thread design. Thus, a user must purchase both a new weight bar and a matching set of dumbbells and cannot use dumbbells that they may already own.
In addition, threaded dumbbells often include flat box-shaped thread profiles allowing the load of the added weight plates to be distributed over a relatively large flat surface area, thus preventing undue thread wear and/or cutting into the weight plate. A weight bar having a standard thread profile, with sharp peaks or edges at their thread apex, cannot accept an externally-threaded dumbbell with a flat thread profile.
Accordingly, a need exists for a weight bar that can be used with externally-threaded dumbbells that have the flat thread profile. Furthermore, it may be desirable to have a weight bar that can accept a multitude of flat thread profiles, thus allowing the user of a wider range of existing dumbbells already on the market.